Lubricating greases containing alkylbeta-amino propionates



LUBRICATING GREASES CONTAINING ALKYL- BETA-AMINO PROPIONATES Jeffrey H.- Bartlett, Westfield, and Arnold J. Morway,

Rahway, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application September 30, 1953 Serial No. 383,369

4 Claims. (Cl. 252-33.6)

. No Drawing.

The present invention relates to improved lubricating greases and thickening materials for such greases as well as to a new method of preparing such greases. More particularly the invention relates to novel grease thickeners and greases which have excellent high temperature and channeling characteristics and greatest utility in antifriction bearing lubrication.

In brief compass the invention pertains to a soap type grease thickener containing at least a substantial proportion of a metal soap of an alkyl-beta-amino propionic acid and to greases containing such a thickener. The invention is also concerned with new methods for preparing such acids, soaps and greases.

Channeling greases have long been used in the lubrication of anti-friction bearings such as ball or roller bearings. These greases must provide a low torque and low temperature rise in the bearing and they must have excellent high and low temperature characteristics and a long high temperature lubrication life which makes frequent repacking unnecessary. Where repacking is not possible long economical bearing life is required, which is essential when the bearing is employed in inaccessible places.

The so-called complex soap type greases comply best with these requirements. Such greases are thickened with a soap-type grease thickener which in addition to an alkali or alkaline earth metal soap of a high molecular weight soap-forming carboxylic acid contains combined therewith a salt of a metal with a low molecular weight carboxylic acid having 1-6 carbon atoms, such as formic, acetic, lactic, or similar acid.

Quite generally, the channeling characteristics and the lubricating life of these greases are a function of the soap content. That is, the higher the soap content the better is the channeling quality and the longer the lubrication life of the grease. All these greases have, therefore, a relatively high soap content. However, improvements obtainable in this manner are limited by the hardening effect of excessive soap concentrations.

It has now been found that excellent channeling-type lubrication greases of long lubrication life and highly satisfactory consistency at all temperatures at high soap concentration are obtained when the grease thickener contains at least a substntial proportion say about 20-100 wt. percent of a metal soap of a monoor dialkyl betaamino propionic acid. While all metal bases normally used in grease-making are suitable the alkali and alkaline earth metals are most desirable. It is important that the nitrogen atom carry at least one alkyl group having from about to 30 carbon atoms. When two alkyl groups are present on the nitrogen each may have from 10 to 30 carbons although one may be a short alkyl group such as methyl, ethyl, etc. The alkyl groups are preferably relatively straight chains, especially those having 10 to 30 carbons. However, branched chains are also suitable for certain purposes.

The soaps of monoand dialkyl beta-amino propionic acids may be produced in situ in the grease-making batch 2,882,230 Patented Apr. 14, 1959 ice by hydrolysis of the corresponding nitriles or esters. The alkyl beta-amino propionic nitriles or esters are general- 1y derived from the primary or secondary amines. By treatment of the amines with acrylonitrile, methacrylonitrile, acrylate esters or methacrylate esters the nitrogen addition takes place on the beta carbon atom to the nitrile or carbonyl groups at temperatures of --22 to +392 F. as indicated below.

( CHaCHrCN ll CHzCHnC-OR' (3) RzNH+ CH2=CHGN RaNCHzCHzCN It will be noted that the primary amines yield two products, one having a secondary, the other a tertiary nitrogen atom (Reactions 1 and 2). Both of these products are useful. The secondary amine forms only a single reaction product having a tertiary nitrogen atom (Reaction 3).

Primary and secondary amines from various sources may be .used in the preparation of the alkyl beta-amino propionic esters or nitriles. At present some of the more available amines are those derived from animal or vegetable fats such as tallow, cottonseed oils, soya oil, etc. However, many petroleum fractions may be used in the preparation of the amines, such as the paraflin waxes, white oils, kerosene, gas oil, bright stocks, lubricating oil stocks, polymerized olefins, etc. Generally, it is desirable to use petroleum fractions with low aromatic content.

Consequently acid treatment or solvent extraction of Some of the advantages of the invention may be realized by using metal soaps, particularly alkali metal soaps of alkyl beta-amino propionic acid, as the sole or essentially sole thickener. Soap concentrations of about 20- 30% should be used in this case. However, in accordance with the preferred embodiment of this invention, the alkyl beta-amino propionic acid soap is present in the grease in the form of a complex with a salt, preferably an alkali metal salt, of a low molecular weight carboxylic acid. In many cases, it may be desirable to incorporate into the complex a soap of a high molecular weight fatty acid other than an alkyl beta-amino propionic acid. Thickeners of this type may contain about 20-75 wt. percent, preferably about 25-50 wt. percent, of alkyl beta-amino propionic acid soap. The low molecular weight acid salts and total high molecular weight acid soaps may be present in equi-molecular proportions.

' However, the low molecular weight acid may be present grease. It is, however, a particular advantage of the present invention that excellent channeling greases of soft structure may be obtained even when using the relatively high soap concentrations required to assure long lubrication life. Complex soap concentrations of about to 30 wt. percent are, therefore, preferred.

The low molecular weight acids to be combined with the alkyl beta-amino propionic acids to form the complex soap thickener of the invention may be any aliphatic carboxylic acid having 1-5 carbon atoms per molecule, such as formic, acetic, propionic, butyric, valeric, lactic, furoic, acrylic acids, etc. The preferred low molecular weight acids both from a structural and economic standpoint are formic and acetic acids. High molecular weight fatty acids which may be used together with alkyl beta-amino propionic acid and the low molecular weight acids here specified include saturated or unsaturated fatty acids having 10-30 carbon atoms per molecule, such as hydrogenated fish oil acids, stearic acid, oleic acid, behenic acid, etc., saturated acids having 14-22 carbon atoms per molecule being preferred.

Metal bases suitable for the formation of complex soaps in accordance with the invention include the hydroxides and carbonates of alkali, alkaline earth and certain other metals, for example, lithium, sodium, potassium, calcium, barium and aluminum. However, alkali metal bases, particularly the hydroxides of sodium and lithium, which form complex soaps of satisfactory water solubility and temperature characteristics, are preferred.

Regarding lubricating oil bases suitable for the greases of the invention, all types of mineral lubricating oils as well as synthetic oils including diesters, complex esters, formals and hydrocarbon polymers having lubricating oil characteristics may be used.

Greases in accordance with the invention may be prepared by preforming the alkyl beta-amino propionic acid soap or soap complex with other acids and incorporating the same in the lubricating oil by mechanical mixing. The preformed soap or soap complex may be prepared by neutralizing the alkyl-beta-amino propionic acid or mixtures thereof with the other acids to be used by means of substantially stoichiometric amounts of the desired metal base preferably in aqueous solution, recovering the complex soap formed and compounding the same with the lubricating oil at grease-making conditions.

However, the preferred method of the invention, particularly when minerall ubricating oils are used, involves formation of the soap or soap complex in situ in the lubricating oil in the course of the grease-making process. For this purpose the alkyl-beta-amino propionic acid, its nitrile or ester, and the other high molecular weight fatty acids, if any, may be charged to a reaction zone and heated together with a portion of the lubricating oil to about 130 "-170" F. Thereafter the low molecular weight acid may be added and the mixture neutralized and/or hydrolized preferably with a slight stoichiometric excess of an aqueous solution of the metal base of about 30-50% concentration. Sufiicient metal base should be used to give the grease a free alkalinity of about 0.1-1.5 as NaOH.

The mixture may then be dehydrated at temperatures of about'250-350 F. When dehydration is substantially complete, further lubricating oil may be added and heating continued to about 450-550 F. Thereafter, the grease may be cooled. When temperatures below 300 F. are reached other conventional additives, such as antioxidants, particularly amino compounds, extreme pressure agents containing sulfur, halogen and/ or phosphorus, etc. may be added in any conventional manner.

The invention Will be further illustrated by the following specific example.

EXAMPLE A cyanoethyl tallow amine grease was prepared from the following constituents:

4 Formulation Percent weight Beta cyanoethyl tallow amine 1 10.00 Hydrofol acids 54 2 10.00 Acetic acid (glacial) 4.00 Sodium hydroxide 6.50 Phenyl alpha naphthylamine 1.00

Naphthenic lubricating oil A having a viscosity of S.S.U. at 210 F 28.50 Naphthenic lubricating oil B having a viscosity of 40 S.S.U. at 210 F 40.00

1 Armour & Co. (hemical Division product C1eH2-INHCH2CH2CN Hydrogenated fish oil acids corresponding to commercial stearic acid in degree of saturation.

Preparation Oil A was charged to a fire heated kettle followed by the beta-cyanoethyl tallow amine and the Hydrofol Acids 54. The mixture was warmed to 150 F., and the acetic acid was added, followed immediately by the neutralizing sodium hydroxide in a 40% aqueous solution. Heating was continued as follows:

Time, minutes Temp, F.

Start 170. 60 280. 430. 520--shut off heat and started cooling. -275--added phenyl-u-naphthylamine. 200shut down.

The cooled grease was filtered, Gaulin homogenized at 3000 p.s.i. and packaged.

through bearing seals.

The invention is not limited to the specific figures of the foregoing example. The relative proportions of the grease constituents may be varied within the limits indicated above to obtain greases of different consistency and varying characteristics.

What is claimed is:

1. A lubricant comprising a major proportion of a lubricating oil and in the range of 10 to 40 weight percent of a complex thickener consisting of significant amounts of: (1) a metal salt of a carboxylic acid having in the range of 1 to 5 carbon atoms per molecule, (2) a metal soap of a fatty acid having in the range of 10 to 30 carbon atoms per molecule, and (3) a metal soap of an alkyl-beta-amin0 propionic acid, the alkyl group thereof having in the range of 10 to 30 carbon atoms; the metal component of said soaps and salt being selected from the group consisting of alkali and alkaline earth metals, the propionic acid soap constituting in the range of 20 to 75 Weight percentof said complex thickener and the molar proportion of said salt to said soaps being in the range of 1 to 3.

2. The lubricant of claim 1 wherein said metal component is sodium.

3. The lubricant of claim 1 wherein said oil is a mineral lubricating oil.

4. A method or preparing a lubricant comprising a major proportion of a lubricating oil and in the range of 10 to 40 Weight percent of a complex thickener, which comprises: adding in significant amounts an alkyl-betaamino propionic nitrile, the alkyl group thereof having in the range of 10 to 30 carbon atoms, and a fatty acid having in the range of 10 to 30 carbon atoms per moleculc to said oil, heating the resulting admixture to a temperature in the range of 130 to 170 F., then adding a low molecular Weight carboxylic acid having in the range of 1 to 5 carbon atoms per molecule followed by addition of a suflicient amount of an aqueous solution of a metal base to hydrolyze and neutralize said nitrile and said acids, the metal component of said metal base being selected from the group consisting of alkali and alkaline earth metals, and then heating the neutralized admixture to a complex-forming temperature in the range of 450 to 550 F., the propionic acid soap derived from said nitrile constituting in the range of 20 to 75 Weight percent of said complex thickener and the molar proportion of the salt derived from said low molecular Weight carboxylic acid to the other soaps present being in the range of 1 to 3.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,012 Isbell Apr. 19, 1949 2,468,098 Morway et a1 Apr. 26, 1949 2,614,076 Moore et a1 Oct. 14, 1952 2,614,077 Moore et al Oct. 14, 1952 

1. A LUBRICANT COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL AND IN THE RANGE OF 10 TO 40 WEIGHT PERCENT OF A COMPLEX THICKENER CONSISTING OF SIGNIFICANT AMOUNTS OF: (1) A METAL SALT OF A CARBOXYLIC ACID HAVING IN THE RANGE OF 1 TO 5 CARBON ATOMS PER MOLECULE, (2) A METAL SOAP OF A FATTY ACID HAVING IN THE RANGE OF 10 TO 30 CARBON ATOMS PER MOLECULE, AND (3) A METAL SOAP OF AN ALKYL-BETA-AMINO PROPIONIC ACID, THE ALKYL GROUP THEREOF HAVING IN THE RANGE OF 10 TO 30 CARBON ATOMS; THE METAL COMPONENT OF SAID SOAPS AND SALT BEING SELECTED FROM THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METALS, THE PROPIONIC ACID SOAP CONSTITUTING IN THE RANGE OF 20 TO 75 WEIGHT PERCENT OF SAID COMPLEX THICKENER AND THE MOLAR PROPORTION OF SAID SALT TO SAID SOAPS BEING IN THE RANGE OF 1 TO
 3. 